I. Field and Utility Summary
The invention described herein is a new variety of apple tree, Malus domestica×Malus robusta hybrid, hereinafter referred to as ‘G.814’. The new variety is useful as a dwarfing rootstock and is resistant to fire blight and crown rot. It is precocious and highly productive, and can be used as a rootstock and for interstems of apple trees.
II. Cultivation Summary
‘G.814’ originated from a planned cross in 1976 in Geneva, N.Y.
In the spring of 1976, pollen from a Malus robusta ‘Robusta 5’ apple tree (not patented) was applied to emasculated flowers of a Malus domestica ‘Ottawa 3’ apple tree (not patented) in Geneva, N.Y. In the fall of 1976, seeds resulting from this pollination were extracted from mature fruit derived from this cross. In the winter of 1976-77, the seeds were stratified and planted in large flats under conditions effective to germinate seeds and obtain seedlings. When germinated seedlings were about 2.5 cm tall they were inoculated with a mixture of isolates of the fungus Phytophthora cactorum (the causal agent of crown and root rots). The flats were flooded to mid-hypocotyl level and kept at 23° C. for one week. Surviving seedlings were transplanted into individual pots.
In the summer of 1977, each of the transplanted seedlings was inoculated with approximately 106 colony forming units of the Ea 273 strain of the fire blight bacterium Erwinia amylovora by inserting a 26-gauge hypodermic syringe needle into the shoot tip. The seedling designated as #814 was one of the survivors of this battery of inoculations from the same cross. All the surviving plants were transplanted to a field in Geneva, N.Y. in the fall of 1977. The surviving plants were then allowed to grow side shoots for propagation and evaluation. In 1980, ‘G.814’ was evaluated for rooting ability, lack of spine production, and low root brittleness in a layering bed (stool bed).
In 1984, three finished trees with ‘G.814’ rootstock were planted in a first test orchard in Geneva, N.Y. with Malus domestica cv. ‘Northern Spy’ (not patented) grafted onto this rootstock as the scion cultivar. This rootstock performed well (top 20% of many rootstocks tested) in these first test trials. In 1991, this rootstock was advanced to elite status based on field performance and four trees were planted with Malus domestica cv ‘Empire’ (not patented) for advanced evaluation. This planting was evaluated for twelve years resulting in the classification of ‘G.814’ in the dwarfing category similar to ‘Malling 26’ (not patented) apple rootstock and the cumulative productivity in the top 10% of the planting.
In 1994, an additional experimental orchard was planted in Geneva, N.Y. It featured several trees of ‘G.814’ as the rootstocks with scions ‘Mutsu’ (not patented), ‘Haralson’ (not patented), ‘Royalty’ (not patented), and ‘Radiant’ (not patented) to test the productivity with different scions. The tests resulted in acceptable performance with these scions.
In the spring of 2002, ‘G.814’ and other experimental rootstocks were planted as finished trees with ‘Golden Delicious’ (not patented) scion in Geneva, N.Y. In 2003 and 2004 the orchard was spray inoculated, while in bloom, with fire blight. All trees of ‘G.814’ survived, indicating good resistance of the rootstock in an orchard environment.
In February, 2002, several rootstock liners of ‘G.814’ were budded with Apple Stem Grooving Virus (ASGV) (Capillovirus spp.) infected wood and after the buds were healed the rootstocks were planted in a nursery in Geneva, N.Y. and monitored for survival and stunting. Measurements in August, 2002, showed that 50% of the plants had died and the surviving ones were stunted. These results indicated that this rootstock is susceptible to ASGV.
In summer, 2007, twenty rootstock liners were inoculated with two different strains of fire blight (ten liners per strain) in a greenhouse in Geneva, N.Y. As a result, the apple rootstock ‘G.814’ was classified as resistant to all of the strains tested. Furthermore, ‘G.814’ was observed to be susceptible to wooly apple aphid, resistant to powdery mildew, cold hardy, and tolerant of replant disease.
In the fall of 2005, the tree architecture of nursery trees was measured on ‘G.814’ and found that it promotes higher number of feathers and medium spreading habit on ‘Gala’ (U.S. Plant Pat. No. 03,637) scions.
III. Asexual Reproduction
Asexual reproduction of the ‘G.814’ apple rootstock has been achieved using the traditional method of clonally propagating apple rootstocks. In particular, the original seedling of the ‘G.814’ apple rootstock was planted in Geneva, N.Y., and allowed to develop into a “mother plant.” The ‘G.814’ mother plant was then used to obtain rooted liners using conventional layering procedures. The resulting liners were then planted in a row to generate a layering stool bed (also referred to as the “mother stool bed”). The living tissues (i.e. leaves, stems, roots, buds, and spines) of the mother stool bed were observed to be identical to secondary and tertiary stool bed plants. In addition to conventional layering, the ‘G.814’ variety has been asexually reproduced in Geneva, N.Y., by root cuttings, by budding and grafting onto seedling and clonal rootstocks.
IV. Stability
Observations of trees from propagations in Geneva, N.Y. indicate that all clonally propagated trees have proven true to type and identical in all appearances to the original tree.